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# CCGSEQ -- Routine for computing RA and Dec for a given X,Y pixel
# position on a GSSS image. Adapted from stsdas$pkg/analysis/gasp/gasplib/.
# See stsdas$copyright.stdas for copyright restrictions.
procedure ccgseq (plate_centre_ra, plate_centre_dec, plate_centre_x,
plate_centre_y, x_pixel_size, y_pixel_size, plate_scale, amd_x,
amd_y, object_x, object_y, object_mag, object_col, object_ra,
object_dec)
double plate_centre_ra #I plate Right Ascension (radians)
double plate_centre_dec #I plate Declination (radians)
double plate_centre_x #I x position used in solution (microns)
double plate_centre_y #I y position used in solution (microns)
double x_pixel_size #I scan pixel size in x (microns)
double y_pixel_size #I scan pixel size in y (microns)
double plate_scale #I plate scale (arcsec / mm)
double amd_x[ARB] #I ra plate model coefficients
double amd_y[ARB] #I dec plate model coefficinets
double object_x #I x pixel position for object
double object_y #I y pixel positions for objects
double object_mag #I object magnitude
double object_col #I object colour
double object_ra #O object ra (radians)
double object_dec #O object dec (radians)
double x # position from center (mm)
double y # position from center (mm)
double xi_object # xi standard coordinate (arcsec)
double eta_object # eta standard coordinate (arcsec)
double p1,p2,p3,p4
begin
# Convert x,y from pixels to mm measured from the plate centre
x = (plate_centre_x - object_x * x_pixel_size) / 1000.0d0
y = (object_y * y_pixel_size - plate_centre_y) / 1000.0d0
# Compute standard coordinates from x,y and plate model coefficients
p1 = amd_x(1) *x +
amd_x(2) *y +
amd_x(3) +
amd_x(4) *x**2 +
amd_x(5) *x*y +
amd_x(6) *y**2
p2 = amd_x(7) *(x**2+y**2) +
amd_x(8) *x**3 +
amd_x(9) *x**2*y +
amd_x(10) *x*y**2 +
amd_x(11) *y**3
p3 = amd_x(12) *x*(x**2+y**2) +
amd_x(13) *x*(x**2+y**2)**2 +
amd_x(14) *object_mag +
amd_x(15) *object_mag**2 +
amd_x(16) *object_mag**3
p4 = amd_x(17) *object_mag*x +
amd_x(18) *object_mag*(x**2+y**2) +
amd_x(19) *object_mag*x*(x**2+y**2) +
amd_x(20) *object_col
xi_object = p1 + p2 + p3 + p4
p1 = amd_y(1) *y +
amd_y(2) *x +
amd_y(3) +
amd_y(4) *y**2 +
amd_y(5) *x*y +
amd_y(6) *x**2
p2 = amd_y(7) *(x**2+y**2) +
amd_y(8) *y**3 +
amd_y(9) *y**2*x +
amd_y(10) *y*x**2 +
amd_y(11) *x**3
p3 = amd_y(12) *y*(x**2+y**2) +
amd_y(13) *y*(x**2+y**2)**2 +
amd_y(14) *object_mag +
amd_y(15) *object_mag**2 +
amd_y(16) *object_mag**3
p4 = amd_y(17) *object_mag*y +
amd_y(18) *object_mag*(x**2+y**2) +
amd_y(19) *object_mag*y*(x**2+y**2) +
amd_y(20) *object_col
eta_object = p1 + p2 + p3 + p4
call trsteq (plate_centre_ra, plate_centre_dec,
xi_object, eta_object, object_ra, object_dec)
end
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